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1. Field of the Invention
The present invention relates generally to concrete screeding apparatus for placing, consolidating and finishing plastic concrete. In particular, the present invention relates to an inverted triangular truss modular screed with an outrigger support. Relevant art may be found in U.S. Class, subclasses 101, 114, 115, as well as others.
2. Description of the Known Art
As will be appreciated by those skilled in the art, wet or plastic concrete must be worked before it sets and forms a hardened slab. Working plastic concrete generally involves consolidating the plastic concrete to evenly distribute water and aggregates throughout the resulting monolith and, subsequently, leveling and finishing the consolidated plastic concrete to appropriately contour the top layer of the plastic concrete.
Consolidating plastic concrete is often performed by vibrating the plastic concrete to evenly distribute water and aggregate materials throughout the monolith of concrete. The vibrations also fracture air pockets trapped inside the monolith and permit the air to escape therefrom. Other pockets of materials, such as sand and gravel or the like, are also shattered so that their components may be more evenly distributed throughout the monolith.
Several tools have been previously proposed for working plastic concrete. These tools include screeds, trowels (both manual and self-propelled), and other tools such as floating pans and the like. Of the former, screeds with strike-offs are commonly employed during initial plastic concrete consolidation while the other types are typically used to finish the top surface of the concrete to a desired smoothness.
Form riding screeds are typically at least ten feet in length and ride upon the forms bounding the concrete monolith. These form-riding screeding apparatus are usually pulled along the form by a series of cables or the like and generally employ remote power to vibrate the smoothing blade. Examples of conventional form-riding screeds are shown in U.S. Pat. Nos. 3,299,786 and 3,541,931.
Screeds may generally be grouped according to the number of operators needed to operate them, support mechanisms necessary for their proper operation, structural shapes, or other meaningful characteristics. It is not uncommon for a screed to meet the criteria for several groups. Screeds with strike-offs are normally employed in xe2x80x9cwetxe2x80x9d plastic concrete to initially level and consolidate the monolith because the wet plastic concrete typically will not support heavy weights. (xe2x80x9cWetxe2x80x9d plastic concrete generally has a slump of between three and ten inches.)
Exemplary multiple operator screeds are shown in U.S. Pat. Nos. 3,110,234, 3,299,786, 3,541,931 and 3,593,627. These devices generally strike-off, vibrate and level plastic concrete in a single pass. They may employ remote power and are typically drawn through plastic concrete by multiple operators. However, they are large and unwieldy and they often require excessive site preparation and cannot be moved quickly about the pour. These devices also suffer from other handicaps associated with maintenance and the like. The configuration of their truss system is such that the vibratory mechanism and strike off blades are essentially an integral part of the screed. As a result of this configuration, the vibrations shake the entire unit, which makes continuous adjustment of alignment characteristics during the screeding operation a matter of course. The concrete leveling blades need to be changed to provide for different finish textures and the like. The strike-off blades occasionally need to be changed to accommodate different plastic concrete mixes. As will be appreciated by those skilled in the art, changing blades on existing screeds requires considerable time.
U.S. Pat. No. 3,110,234 to Oster shows a concrete screeding machine with a rectangular cross-sectional truss beam. The device employs oppositely moving screeds (rather than vibrating screeds) to eliminate side thrust. The device does not utilize supporting outriggers to prevent sagging or to maintain a selected alignment pitch nor does it utilize an inverted triangle truss to support concrete-finishing elements centrally.
U.S. Pat. No. 3,299,786 to Godbersen shows a bridge deck finisher that utilizes a rectangular cross-section truss beam. The apparatus uses spring urging toward the concrete to provide resiliency. The apparatus does not utilize supporting outriggers to prevent sagging or to maintain a selected alignment pitch nor does it utilize an inverted triangle truss to support concrete-finishing elements centrally.
U.S. Pat. No. 3,541,931 to Godbersen shows a concrete finishing mechanism having an adjustable rotating drum. While this device is of only marginal relevance, it too employs a rectangular cross-section truss beam. The device does not utilize supporting outriggers to prevent sagging or to maintain a selected alignment pitch nor does it utilize an inverted triangle truss to support concrete-finishing elements centrally.
U.S. Pat. No. 3,593,627 to Rowe et al. shows a concrete finishing machine movable longitudinally of a road and having a pair of oppositely reciprocating finishing members movable transversely back and forth across the road. The device utilizes a rectangular cross-section truss beam to support the finishing members. The device employs elongated adjustment rods to enable the device to accommodate crowns on roads. The device does not utilize supporting outriggers to prevent sagging or to maintain a selected alignment pitch nor does it utilize an inverted triangle truss to support concrete-finishing elements centrally.
U S. Pat. No. 5,533,831 to Allen shows an obstacle bypass system for concrete finishing tools. The device utilizes a rectangular cross-section to support the finishing members. The device employs pivoting members to enable the device to retract to bypass obstacles. The device does not utilize supporting outriggers to prevent sagging or to maintain a selected alignment pitch nor does it utilize an inverted triangle truss to support concrete-finishing elements centrally.
U.S. Pat. No. 5,988,939 to Allen et al. shows a universal bridge deck vibrating system that utilizes a translating carriage atop a conventional rectangular cross-sectioned beam screed. The device does not utilize supporting outriggers to prevent sagging or to maintain a selected alignment pitch nor does it utilize an inverted triangle truss to support concrete-finishing elements centrally.
Thus, there exists a need in the art for a vibratory screed that may be easily transported about a pour site as well as from pour site to pour site, with minimal preparation time required before use to consolidate and level plastic concrete. The screed width needs to be easily adjustable to accommodate a large range of spans. The working or finishing tools, such as strike-off blades and leveling bars, need to be easily removable to accommodate various concrete mixes that might be spread and the desired texture of the finished concrete monolith. A particularly advantageous apparatus would use a dependable vibratory dispersion system that dampens vibration transmission to the truss system while preventing undesirable down time for camber or pitch adjustments to promote efficient concrete consolidation and leveling.
A need also exists for an improved multiple operator vibratory concrete screeding apparatus that has vibration dampening between the vibratory mechanisms and the trussed beam, has easily changeable strike-off and leveling blades, and has easily adjustable alignment mechanisms, especially for pitch camber alignment.
In accordance with one exemplary embodiment of the present invention, a screed with a trussed main beam having a cross-section in the geometrical shape of an equilateral triangle is used for finishing concrete. This beam is oriented such that the equilateral triangle is turned upside down or inverted with the wide base at top and the bottom pointed toward the concrete being worked upon below the screed. The inverted triangular truss beam gives sufficient space to mount working tools, such as a leading scraper or strike-off or leveling blade as well as a trailing smoothing tool or bar more closely within or substantially within the peripheral edges of the screed beam rather than being placed a substantial distance in front or behind the main screed beam. In this position, the tools or blades are stabilized by the weight of the beam and do not unduly torsion the supporting truss system. This reduction in torsion is primarily due to reduction in the lever multiplier effect for locations forward or behind the screed beam.
The screed has several primary members including carriage assemblies, a concrete spanning beam from which tools are suspended and uprising outriggers. The screed is adapted to be used to work plastic concrete to produce a desirably formed monolith in a single pass. The screed rides on forms bounding the plastic concrete on spaced apart, wheeled end carriage assemblies. The main trussed beam extends between the carriage assemblies and it is thus supported over the plastic concrete to be worked.
In use, the carriage assemblies ride on the forms bounding a concrete pour site while the beam passes over the concrete therebetween. Any tools suspended by the beam can thus work on the concrete passing beneath the beam in a conventional fashion to produce a desirably finished concrete monolith.
Usually only one concrete finishing tool is mounted before and one aft of the main trussed beam. As a result of the particular geometry of the inverted triangle truss beam, there is sufficient space on the quick connector to mount additional concrete finishing tools if desirable.
The main beam has spaced apart ends, each of which include a terminal steel plate that has the same dimensions as the trussed beam and which mate with corresponding coupling points on each carriage. At each beam end, an outrigger assembly is captivated between the beam end and the carriage assembly.
Each outrigger includes a front and rear stanchion. Each stanchion rises above the plane of formed by the truss base. A front and rear adjustment bar extends inwardly from the front and rear stanchion to a point proximate the beam midpoint where they are anchored to the beam. The front and rear adjustment bars may be selectively lengthened or shortened to change the pitch or alignment of the screed to vary the angle of attack for the suspended tools or the resultant shape of the concrete monolith produced by the screed.
The terminal beam plates and the other primary members have triangular slots adapted to receive short alignment members that facilitate coupling abutting members. Thus, the primary members may be transported in an unassembled state and quickly assembled at a job site.
In one exemplary embodiment in accordance with the present invention, the main trussed beam includes several sections of modular design. The sections or modules can include only the main beam or they can include concrete finishing tools. The latter is preferential since at a minimum each main trussed beam module will have a leading working tool such as a scraper or strike-off blade and a finishing tool such as a vibrator or a vibrator bar attached. Individual modules can range from 2.5 feet to 10 feet in width. As a result of the different sizes, combinations of modules can be assembled in any configuration to meet the width requirement of the job at hand. The ends of the modules are shaped for quickly attaching one to another in their central trussed beam geometry. The modules are coupled together with bolts through holes in their respective steel end plates.
The ends of each main beam module have reinforcing steel bands located next to the steel end plate. Longer modules can have these reinforcing bands spaced along them. In addition to providing extra strength, these bands can serve as attachment locations both in front of as well as behind the main trussed beam for xe2x80x9cquick connectingxe2x80x9d concrete finishing tools. This xe2x80x9cquick connectionxe2x80x9d utilizes a common geometrical configuration for attaching concrete finishing tools to the main inverted triangle trussed beam which results in a system that makes attaching various concrete finishing tools to the inverted triangle trussed beam simplistic. In one exemplary embodiment, the common geometrical configuration is a bracket that has a cross section in the shape of an equilateral triangle whose dimensions are determined by the distance in front of or behind the main beam it is desired for the concrete finishing tool to operate as well as their mounting height.
In addition, the leveling blade as well as the vibratory bar may each be attached with only one bolt at each reinforcing band of a main beam module. Anti-vibration components can be included as desired at the points of attachment of vibratory bars to the xe2x80x9cquick connectorxe2x80x9d framework as well as where the xe2x80x9cquick connectorxe2x80x9d attaches to the main trussed beam. Vibration control is further enhanced by isolating the source of the vibration by having small vibrators mounted on the vibratory bar for each module.
During setup, the inverted triangle trussed beam screed is aligned and adjusted to give the desired surface crown. Even with the dampened vibrations acting on the screed, the vibrations are such that the screed can be shaken out of alignment. Thus, continual alignment adjustments may need to be made during operation. Since the screed has outriggers, the pitch or alignment of the screed can be adjusted outside of or exteriorly from the pour site. Thus, the operator is not required to walk through the plastic concrete to make these adjustments. This is preferential since walking through the plastic concrete is to be avoided as it disturbs the concrete by leaving depressions and imperfections in the concrete or it slows the process by stopping the forward movement of the screed. The outriggers also support the center of the screed from the outer edges of the screed, which is especially important for longer spans.
Thus, a principal object of the present invention to provide a concrete leveling and finishing apparatus that enhances and improves concrete leveling and finishing operations.
A basic object of the present invention is to provide a concrete finishing apparatus for which a selected pitch may be easily implemented and maintained.
Another basic object of the present invention is to provide a concrete finishing device that minimizes torsion stresses by positioning leading and trailing tools centrally.
Another object of the present invention is to provide substantial weight reduction in a concrete screeding apparatus without a reduction in its strength.
Yet another object of the present invention is to provide a method of adjusting the pitch of a screed without requiring operators to enter poured plastic concrete.
Another object of the present invention is to provide a method of quickly changing the leveling blades and smoothing bars of a concrete finishing apparatus.
Yet another object of the present invention is to provide a means for dampening vibrations upon a concrete finishing apparatus.
A further object of the present invention is to provide a means to accommodate various span widths by using module units of various lengths that can be assembled in any order or combination.
An object of the present invention is to provide a concrete finishing apparatus that can be assembled and disassembled rapidly to facilitate transport among job sites.
These and other objects and advantages of the present invention, along with features of novelty appurtenant thereto, will appear or become apparent in the course of the descriptive sections.